The invention relates to a device for producing drilled holes with an undercut, especially in facing panels, comprising an adaptor having a drilling tool at the free end thereof, a bearing bush, and a sleeve having a circumferential collar and pivotally received within the bearing bush.
Devices to produce drilled holes with an undercut and having a bearing bush with a concave depression in which a drilling tool provided with a collar is supported and pivotally mounted are known. By pivoting-out the drilling tool while simultaneously moving it with a circular motion, an undercut in the region of the bottom of the drilled hole, into which an expansible fixing plug with an expansible sleeve can be inserted with a matching fit, is reamed out with lateral cutting edges of the drilling tool.
Such drilled holes with an undercut can also be made in facing panels or similar structures. However, in that case, the undercuts have to be made very precise, so that when inserting and expanding an expansible anchor, the expansion pressure that is generated is not too big. Too big an expansion pressure can result in a part of the facing panel breaking away. In order to produce a precise undercut, drilling tools which have a drilling head tipped with diamond chips are used. The known constructions for forming a pivot bearing bush are neither adequate for these impact-susceptible and shock-susceptible drilling tools, nor for the required accuracy of the undercut drilled holes in thin-walled facing panels.